package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;
import static java.util.concurrent.Executors.*;

/**
 * @author 86178
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {

        //缓存穿透(在下面的queryWithMutex中已经解决，且queryWithMutex使用了互斥锁解决了缓存击穿，所以用下面的API)
//        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, id2 -> getById(id2)
//                , CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, id2 -> getById(id2), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        //返回数据
        return Result.ok(shop);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = newFixedThreadPool(10);

    /**
     * 利用逻辑过期解决缓存击穿以及解决缓冲穿透
     *
     * @param id
     * @return
     */
    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断商铺是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.不存在，直接返回空
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回店铺信息
            return shop;
        }
        //5.2已过期，则进行缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if (isLock) {
            //TODO 6.3成功，开启一个独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException();
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4获取失败，直接返回过期的商铺信息
        return shop;
    }

    /**
     * 利用互斥锁解决缓存击穿以及解决缓冲穿透
     *
     * @param id
     * @return
     */
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断商铺是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            System.out.println("1存在");
            return shop;
        }
        //判断命中的是否为空值，如果不是空值，代表为""，这时候为了防止缓存穿透，直接返回
        if (shopJson != null) {
            //返回 null
            return null;
        }
        //开始实现缓冲重建
        //4.不存在，根据id查询数据库
        //4.1获取互斥锁
        String lockKty = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKty);
            //4.2判断是否获取成功
            if (!isLock) {
                //4.3失败，则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //4.4成功，根据id查询数据库
            shop = getById(id);
            //模拟重建的延时
            Thread.sleep(200);
            //5.不存在，返回数据
            if (shop == null) {
                //将空值写入到redis中 并设置TTL为2分钟
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回 null
                return null;
            }
            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException();
        } finally {
            //7.释放互斥锁
            unlock(lockKty);
        }

        //8.返回
        return shop;
    }

    /**
     * 解决缓存穿透
     *
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断商铺是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否为空值，如果不是空值，代表为""，这时候为了防止缓存穿透，直接返回
        if (shopJson != null) {
            //返回 null
            return null;
        }
        //实现缓存重建
        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.不存在，返回数据
        if (shop == null) {
            //将空值写入到redis中 并设置TTL为2分钟
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回 null
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id, Long expireSecond) throws InterruptedException {

        //1.查询店铺信息
        Shop shop = getById(id);
        //测试用
        Thread.sleep(200);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSecond));

        //3.写入redis中
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));

    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        boolean update = updateById(shop);
        System.err.println("success:" + update);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
